Rechargeable batteries are used in a wide variety of portable devices such as laptop computers, cellular telephones, personal digital assistants (PDAs), etc. With the rapid increase in portable device technology, it is fairly common for users to replace their portable devices at frequent intervals. However, users may be required to also purchase new battery chargers when upgrading portable devices, because of different connector types or battery types used for different portable devices.
In some cases, the use of standardized interfaces or connectors for portable devices allows a single battery charger to be used for charging different portable devices. For example, many portable devices now support the universal serial bus (USB) protocol, and include one or more USB connectors which allow them to be connected to personal computers (PCs), etc. Further details regarding the USB protocol and connectors may be found in the Universal Serial Bus Specification, Revision 2.0, Apr. 27, 2000, published by USB Implementers Forum, Inc., which is hereby incorporated herein in its entirety by reference. Thus, a charger having a USB connector could potentially be used to charge different portable USB devices.
An example of such a charger is disclosed in U.S. Pat. No. 6,184,652 to Yang. This patent is directed to a mobile phone battery charger with a USB interface that includes a USB compatible plug, a DC converter, and a mobile phone battery charging plug. The USB compatible plug is inserted into a corresponding USB connector of a computer and receives electrical power therefrom. The DC converter converts the electrical power into the necessary charging voltage, which is provided to the mobile phone by the battery charging plug. The battery charger may also detect the type of mobile phone battery (e.g., Li or Ni-MH) and the quantity of electricity or charge stored in the battery. The patent states that a user accordingly need not purchase different kinds of chargers for different battery types.
Another example is disclosed in U.S. Pat. No. 6,362,610 to Yang. More particularly, this patent discloses a universal USB power supply unit which includes a USB port connector and a charging connector. The USB port connector plugs into the jack of the USB port, while the charging connector plugs into the jack of an electronic product to be charged. The current flowing into the USB port connector will then pass through an automatic voltage regulator. Disposed within a housing of the automatic voltage regulator is a DC voltage transformer which transforms the DC voltage (e.g., 5 V) coming from the USB port to the requisite voltage supplied to a power/signal connecting jack. A feedback control voltage output circuit compares the feedback voltage signal of the power/signal connecting jack and enables the DC voltage transformer to output a preset voltage. The charging connector is fitted with a power cord which includes a power/signal connector to fit the power/signal connecting jack. Moreover, a voltage parameter associated with the particular electronic device is preset within the charging connector using a variable resistor.
Despite the advantages of such chargers, problems may still arise when different types of batteries are interchanged in different portable devices. That is, different rechargeable batteries may have different charging parameters (e.g., voltage rating, current rating, etc.). Yet, these parameters may not always match with those of a given portable device. Accordingly, using chargers such as those described above where the battery and device charging parameters are not carefully matched could result in damage to the device and/or battery.